The present invention relates to vehicles of the type that include an internal combustion engine, a cranking motor, and a battery normally used to power the cranking motor. In particular, this invention relates to improvements to such systems that increase of the reliability of engine starting.
A problem presently exists with vehicles such as heavy-duty trucks. Drivers may on occasion run auxiliary loads excessively when the truck engine is not running. It is not unusual for heavy-duty trucks to include televisions and other appliances, and these appliances are often used when the truck is parked with the engine off. Excessive use of such appliances can drain the vehicle batteries to the extent that it is no longer possible to start the truck engine.
The present invention solves this prior art problem in a cost-effective manner.
The preferred embodiment described below supplements a conventional vehicle electrical system with a capacitor. The capacitor is protected from discharging excessively when auxiliary loads are powered, and it is used to supply a cranking current in parallel with the cranking current supplied by the vehicle battery to ensure reliable engine starting. When the vehicle engine is not running, the capacitor is isolated from the vehicle electrical system by an open-circuited relay, and this relay is controlled by a control circuit that itself draws power from the capacitor. In this way, power is always available when the capacitor is charged to close the relay when power is needed for engine cranking. This section has been provided by way of general introduction, and it is not intended to narrow the scope of the following claims.